The present invention relates to an audio-video synchronous playback control system and an audio-video synchronous playback control method for decoding and playing back audio data and video data maintaining synchronization between the audio data playback and the video data playback, and in particular, to an audio-video synchronous playback control system which outputs coded audio data to an external audio decoding device of an external audio output device so that the coded audio data will be decoded and played back by the external audio decoding device while playing back video data maintaining synchronization between the audio data playback and the video data playback, and an audio-video synchronous playback control method for the audio-video synchronous playback control system.